When wiring a house or a building the coax cable network is installed prior to the mounting of the dry wall being, and the network installation is completed after the dry wall has been finished. Accordingly, a technician is faced with a bundle of unlabeled cables hanging in a wiring closet, and their task is to identify each cable, label them, and connect them to the appropriate service. Install technicians from service providers are faced with a similar problem when installing a new service in a home. Typically, there is a group of cables that enter at a side of a house which terminate somewhere within the house, and it is important for a technician to be able to quickly and positively identify where each cable goes, so that new devices and services can be installed quickly and correctly.
Currently resistive based devices are used to perform the task of cable identification; however, in coax based systems, splitters prevent this technique from working effectively. Moreover, resistive devices are limited to less than thirty unique identifiers. Conventional systems that are able to work through splitters are based on active devices that are large, expensive and require batteries.
Conventional RFID systems include RFID tags positioned on everything from employees badges to carcasses of meat, and RFID readers positioned at specific stations or points of entry for reading the RFID tags, as they pass by in close proximity thereto. The RFID tags provide specific information about the item they are attached to the RFID reader to store, tabulate or act upon, e.g. allow access.
RFID tags are tiny microchips with memory and an antenna coil, which can be thinner than paper, e.g. only 0.3 mm across. RFID tags listen for a radio signal sent by the RFID reader. When an RFID tag receives the radio signal query, it responds by transmitting a unique identification code and other data back to the RFID reader.
There are two types of RFID tags: passive RFID tags, and active RFID tags. Passive RFID tags can be as small as 0.3 mm and don't require batteries, as they are powered by the radio signal of the RFID reader, which “wakes them up” to request a reply. Passive RFID tags can be read from a distance of about 20 feet. Semi-passive RFID tags contain a small battery that boosts the range. Passive tags are generally read-only, meaning the data they contain cannot be altered or written over. Active RFID tags, also called transponders, because they contain a transmitter that is always “on”, are powered by a battery, about the size of a coin, and are designed for communications up to 100 feet from the RFID reader. Active RFID tags are larger and more expensive than passive RFID tags, but can hold more data about the product, and are commonly used for high-value asset tracking. Active RFID tags may be read-write, i.e. data contained therein can be written over.
RFID readers are used to query RFID tags in order to obtain identification, location, and other information about the device or product to which the tag is attached. RF energy from an antenna on the RFID reader is collected by the antenna on the RFID tag and used to power up the microchip on the RFID tag.
There are two types of RFID readers: RFID read-only readers and RFID read-write readers. RFID read-only readers can only query or read information from a nearby RFID tag, and are found in fixed, stationery applications, as well as portable, handheld varieties. RFID read-write readers, also known as encoders, read and also write, i.e. change, information in an RFID tag. Such RFID encoders can be used to program information into a “blank” RFID tag. A common application is to combine an RFID reader with a barcode printer to print “smart labels”, which contain a UPC bar code on the front and an RFID tag embedded on the back.
The antennas on the RFID reader and the RFID tag each have a coil, which together form a magnetic field. The RFID tag draws electrical energy from this field, which powers the microchip therein. The microchip then changes the electrical characteristics of the tag antenna, which are sensed up by the reader antenna and converted into a serial number for the RFID tag
There are 4 major frequency ranges that RFID systems operate at. Normally, low-frequency systems are distinguished by short reading ranges, slow read speeds, and lower cost. Higher-frequency RFID systems are used in which longer read ranges and fast reading speeds are required, e.g. vehicle tracking and automated toll collection. Microwave frequencies requires the use of active RFID tags.
Low-frequency3 feet$1+Pet and ranch animal identification;125-148 KHzcar keylocksHigh-frequency3 feet$0.50library book identification;13.56 MHzclothing identification; smart cardsUltra-high freq25 feet $0.50Supply chain tracking:915 MHzBox, pallet, container, trailertrackingMicrowave:100 feet $25+Highway toll collection;2.45 GHzvehicle fleet identification
The 13.56 MHz solution was developed in an effort to lower the cost of RFID tags, and address applications of high quantity tags usage. At 13.56 MHz, a tag's antenna coil need not be made of hard copper wrappings, and can actually be a printed ink on a paper-like substrate, to which an EEPROM is added. Typical applications include: library books, laundry identification, access control, OEM applications.
Both power and bi-directional communications form the air interface between the RFID tags and the reader device. It is the flexibility of the interface to select one or two sub-carriers when communicating from RFID tags to reader device, whilst also using slow or fast data rates from the reader device to the RFID tags, that allows systems to be tuned to suit different operational requirements ranging from use with high RF noise at short range to low RF noise at long range. ISO/IEC 15693 forms part of a series of International Standards that specify a vicinity or contactless tag. ISO/IEC 15693-2:2006 defines the power and communications interface between the tag and the reading device. Other parts of ISO/IEC 15693 define the physical dimensions of the tag and the commands interpreted by the tag and reading device.
Published WIPO Application WO90/16119, entitled Cable Identification System and Method, filed by Brent James, teaches probing each individual coaxial cable at the junction box using a one-to-one communication protocol powered by DC electricity. Unfortunately, the reading device is unable to supply DC power to a plurality of identification devices across a splitter, which is AC coupled. Consequently, the James reference teaches probing one RFID at a time with DC power and with no splitters in the line, whereby sufficient power is available from the test meter to operate the RFID.
An object of the present invention is to overcome the shortcomings of the prior art by providing a passive RFID device to identify installed cables even if the cable has splitters or actives inline using a communication protocol enabling many devices to be read simultaneously. Accordingly, all the identification devices on all the coaxial cable ends can be probed in a single operation.